Clouds

Clouds are formed when relatively moist air ascends, the lower pressures prevailing at higher levels allow expanding, the air cools adiabatically (i.e., without heat exchange with the surrounding air) until its temperature falls below the dew point, consist entirely of water droplets, entirely of ice crystals, or of a mixture of water droplets and ice crystals, with crystals predominating in the colder, upper regions of the cloud temperature below clouds the ice crystals will grow preferentially with respect to the water droplets as water vapour evaporates from the droplets and deposits onto only short times before becoming all ice crystals.